1. Field of the Invention
The present invention relates to an electrophotographic photosensitive member, and a process cartridge and an electrophotographic apparatus having an electrophotographic photosensitive member.
2. Description of the Related Art
As electrophotographic photosensitive members used for process cartridges and electrophotographic apparatuses, electrophotographic photosensitive members containing an organic photoconductive substance have been broadly used in the market at present. The electrophotographic photosensitive member generally has a support and a photosensitive layer formed on the support. Then, an undercoating layer is provided between the support and the photosensitive layer in order to suppress the charge injection from the support side to the photosensitive layer (charge generating layer) side and to suppress the generation of image defects such as fogging.
Providing an undercoating layer, however, is liable to generate a potential variation in repeated use due to a resistance variation of the undercoating layer. Then, a technology to suppress the potential variation is disclosed in which an electron transporting substance is incorporated in an undercoating layer to thereby make the undercoating layer as a layer having an electron transporting capability (hereinafter, also referred to as an electron transporting layer). A technology is simultaneously proposed in which in order that an electron transporting substance does not dissolve out in formation of a photosensitive layer formed on an undercoating layer, in the case where the electron transporting substance is incorporated in the undercoating layer, the undercoating layer uses a curable material which is hardly soluble to a solvent of a coating liquid for the photosensitive layer.
Japanese Patent Application Laid-Open No. 2009-505156 discloses a condensed polymer (electron transporting substance) having an aromatic tetracarbonylbisimide skeleton and a crosslinking site, and an electron transporting layer containing a polymer with a crosslinking agent. Japanese Patent Application Laid-Open No. 2003-330209 discloses that a polymer of an electron transporting substance having a non-hydrolyzable polymerizable functional group is incorporated in an undercoating layer.
However, as a result of studies by the present inventors, it has been found that in the case where an undercoating layer is made to be an electron transporting layer, and a positive charge is applied on an electrophotographic photosensitive member, a positive memory image is generated by a positive charge remaining in the electron transporting layer in some cases. The positive memory image in an electrophotographic apparatus refers to an image in which the application of a positive charge on an electrophotographic photosensitive member in the rubbing time by transfer and cleaning units causes a potential difference between applied portions and non-applied portions and thereby generates a phenomenon of raising the image density.
Since the technologies disclosed in Japanese Patent Application Laid-Open Nos. 2009-505156 and 2003-330209 use a curable material for their electron transporting layer, the homogeneity of a charge transporting structure of the electron transporting layer decreases and the positive memory image is liable to occur in some cases, which have room for improvement.